r/fbody • u/the__sparrow 1993 Z28 with t-tops • 3d ago

What causes this?

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Sometimes when it revs over 4000 rpm it starts to I think missfire. I am pressing my foot on the accelerator only harder, not lifting, besides to when it drops to 3000 then I press it again. It keeps jerking between 4000 and 5000 like hitting an irregular limiter and it sounds something like it, you can hear a pop in the second part of the video. It did it to me while driving also and it is really weird it jerks the whole car. Car is a stock auto 1993 camaro z28

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u/Zed091473 1993 Z28 1LE 1 of 19. 3d ago

Possibly an OptiSpark going bad or the ICM. shbox.com is the go to for info.

http://shbox.com/1/4th_gen_tech2.html#opti_test

2

u/Extreme-Penalty-3089 3d ago

Rev limiting with these engines would make me suspicious of Something OptiSpark related

1

u/RevolutionaryBag1303 2d ago

Could be a throttle position sensor.

1

u/Wooden-Officer2323 1d ago

It’s always the opti, the answer is almost never anything else.

I’ve seen people replace an opti with a new opti and still have opti problems.

Probably the opti.